import java.util.LinkedList;

public class myLinkedList {

    static class ListNode {
        public int val;
        public ListNode prev;
        public ListNode next;
        public ListNode(int val) {
            this.val = val;
        }
    }
    public ListNode head;
    public ListNode last;

    //头插法
    public void addFirst(int data){
        ListNode node = new ListNode(data);
        if(head == null) {
            head = node;
            last = node;
            return;
        }
        node.next = head;
        head.prev = node;
        head = node;

    }
    //尾插法
    public void addLast(int data) {
        ListNode node = new ListNode(data);
        if(head == null) {
            head = node;
            last = node;
            return;
        }
        last.next = node;
        node.prev = last;
        last = node;
    }
    public void checkIndex(int index) {
        if(index < 0 || index > size()) {
            throw new indexNotLegalException("下标不合法!");
        }
    }
    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data) {
        checkIndex(index);
        if(index == 0) {
            addFirst(data);
            return;
        }
        if(index == size()){
            addLast(data);
            return;
        }
        ListNode node = new ListNode(data);
        ListNode cur = head;
        while(index != 0) {
            cur = cur.next;
            index--;
        }

        ListNode prev = cur.prev;
        prev.next = node;
        node.next = cur;
        node.prev = prev;
        cur.prev = node;

    }
    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key) {
        ListNode cur = head;
        while(cur != null) {
            if(cur.val == key) {
                return true;
            }
            cur = cur.next;
        }
        return false;
    }
    //删除第一次出现关键字为key的节点
    public void remove(int key) {

        if(head.val == key) {
            head = head.next;
            //防止只有一个节点
            if(head != null) {
                head.prev =null;
            }

            return;
        }

        ListNode cur = head;
        while(cur != null) {

            if(cur.val == key) {
                cur.prev.next = cur.next;

                if(cur.next != null){
                    cur.next.prev = cur.prev;
                }else {
                    last = cur.prev;
                    last.next = null;
                }

                return;
            }
            cur = cur.next;
        }

    }
    //删除所有值为key的节点
    public void removeAllKey(int key) {
        ListNode cur = head;
        while(cur != null) {
            if(cur.val == key) {
                //是头结点
                if(cur == head) {
                    head = head.next;
                    //只有一个节点
                    if(head != null) {
                        head.prev =null;
                    }
                }else {
                    cur.prev.next = cur.next;
                    if(cur.next != null) {
                        //不是尾巴节点
                        cur.next.prev = cur.prev;
                    }else {
                        //删除的尾巴节点
                        last = cur.prev;
                    }
                }
            }
            cur = cur.next;
        }
    }
    //得到单链表的长度
    public int size() {
        int count = 0;
        ListNode cur = head;
        while(cur != null) {
            count++;
            cur = cur.next;
        }
        return count;
    }

    public void display() {
        ListNode cur = head;
        while(cur != null) {
            System.out.print(cur.val + " ");
            cur = cur.next;
        }
    }
    public void clear() {
        ListNode cur = head;
        while(cur != null) {
            ListNode curNext = cur.next;
            cur.next = null;
            cur.prev = null;
            cur = curNext;
        }
        head = null;
        last = null;
    }
}
